1. Field of the Invention
The present invention relates to an imaging apparatus, and, more particularly, to a method of estimating an amount of available ink contained in an ink reservoir.
2. Description of the Related Art
Ink jet disposable printhead cartridges include an ink reservoir that contains ink that is used to print on a print medium, such as paper. Typically, the ink level indicators on the printer in the Windows driver can keep track of the ink level based on counting the ink drops jetted on the print medium. In addition, the drops jetted during a printhead maintenance operation can be tracked as well. However, ink volume losses can occur in ways that cannot be tracked by only counting jetted ink dots. As used herein, the terms “ink dots” and “ink drops” are synonymous.
For example, it has been recognized that a significant loss of ink volume in a printhead cartridge can occur through evaporation. The evaporation occurs through the vent in the cartridge lid, through the nozzle openings in the printhead nozzle plate (even when capped), through the plastic cartridge body and through the cap seals. The loss rate depends, for example, on temperature and humidity, as well as the construction of the lid vent, cartridge material, etc.
What is needed in the art is a new method of estimating an amount of available ink contained in an ink reservoir that improves on prior methods that rely only on a counting of ink drops expelled from an ink reservoir, such as for example, by accounting for an estimated evaporation loss.